There is a need for improved encapsulation devices for implantation in vivo. In particular, there is a need for devices which are simple to manufacture, but which have improved biocompatibility compared to existing devices. Moreover, there is a need for devices which improve the viability, maturation and/or differentiation properties and function of biological agents such as encapsulated cells following implantation.
Various biological agents, including cells, can be encapsulated within an implant device comprising a semi-permeable membrane and implanted in vivo. The semi-permeable membrane typically permits access of nutrients, growth factors and small biological agents to the encapsulated cells, but prevents access of cells of the immune system. The semi-permeable membrane also prevents egress of the cells from the encapsulation device. A further function of the implant may be to promote vascularization around the device, in order to increase survival of the cells. Suitable implant devices for encapsulating cells are disclosed, for example, in U.S. Pat. No. 6,060,640 and U.S. Pat. No. 6,773,458.